Simplified Model for ASM Dynamics

2011 ◽  
Author(s):  
A. M. Al-Jumaily ◽  
Y. Du
Keyword(s):  
Dynamic Response ◽  
Finite Length ◽  
Smooth Muscles ◽  
Low Frequency ◽  
Length Change ◽  
Simplified Model ◽  
Frequency Range ◽  
Cycling Rate ◽  
Cross Bridge ◽  
Length Changes

The dynamic response of contracted airway smooth muscles to a finite length change and longitudinal oscillations is described using a simplified model. The model is intended to interpret the biophysical events but not to accurately describe them. It shows that the value of tissue length changes have pronounced indications of cross-bridge detachment. However, the frequency of oscillations represents the velocity of the length change, which affects the cross-bridge cycling rate reflected in the low frequency range.

scholarly journals Implementation of the Spectral Method for Determining of Measuring Instruments' Dynamic Characteristics

2020 ◽  
Vol 11 (2) ◽  
pp. 155-162
Author(s):  
A. F. Sabitov ◽  
I. A. Safina
Keyword(s):  
Dynamic Response ◽  
Spectral Method ◽  
Amplitude Spectrum ◽  
Low Frequency ◽  
Signal Amplitude ◽  
Measuring Instruments ◽  
Frequency Noise ◽  
Frequency Range ◽  
Calculated Amplitude ◽  
Zero Frequency

The spectral method for establishing dynamic response of measuring instruments basically requires determining the amplitude spectrum of the signal in its informative part that includes the amplitude spectrum at zero frequency. The operating frequency range of existing low-frequency spectrum analyzers is above zero frequency that leads to an uncertainty in dynamic response of measuring instruments determined by the spectral method. The purpose of this paper is to develop a program for calculating the signal amplitude spectrum, starting from zero frequency, to implement a spectral method for determining the dynamic response of measuring instruments on computers equipped with the MatLab package.To implement the spectral method for determining the dynamic response of measuring instruments, we developed a program in the MatLab 2013b environment that determines the signal amplitude spectrum from zero Hertz. The program reads the source data from Excel tables and presents the calculated amplitude spectrum as a chart and a report table.It is shown that the developed program calculates the signal amplitude spectrum with a standard deviation of not more than 3.4 % in the frequency range of 0 to 10 rad/s. The calculated amplitude spectrum allows determining the time constant of first-order aperiodic measuring instruments with an uncertainty of not more than 0.166 % at any noise level, if their frequencies are outside the information part of the spectrum.We demonstrated the claimed advantage of the spectral method for determining dynamic response using the developed program by the example of a high-frequency noise in the transient response of some measuring instruments.

scholarly journals Asymptotics of eigenfrequencies in the dynamic response of elongated multi-structures

2011 ◽  
Vol 468 (2138) ◽  
pp. 378-394 ◽  
Author(s):  
M. Brun ◽  
G. F. Giaccu ◽  
A. B. Movchan ◽  
N. V. Movchan
Keyword(s):  
Dynamic Response ◽  
Elastic System ◽  
Low Frequency ◽  
Design Tool ◽  
Asymptotic Estimates ◽  
Bridge Structure ◽  
Frequency Range ◽  
Floquet Waves ◽  
Asymptotic Optimization ◽  
Analytical Formulae

The paper addresses a mathematical model describing the dynamic response of an elongated bridge supported by elastic pillars. The elastic system is considered as a multi-structure involving subdomains of different limit dimensions connected via junction regions. Analytical formulae have been derived to estimate eigenfrequencies in the low frequency range. The analytical findings for Bloch–Floquet waves in an infinite periodic structure are compared with the finite element numerical computations for an actual bridge structure of finite length. The asymptotic estimates obtained here have also been used as a design tool in problems of asymptotic optimization.

Dynamic Analysis of Tram Vehicles Coupled With the Track System Based on Staggered Iterative Algorithm

2020 ◽  
Vol 15 (6) ◽  
Author(s):  
Yao Shan ◽  
Binglong Wang ◽  
Shunhua Zhou ◽  
Jiawei Zhang ◽  
Aijun Huang
Keyword(s):  
Dynamic Response ◽  
Soft Soil ◽  
Low Frequency ◽  
Vehicle Body ◽  
Frequency Range ◽  
Fe Method ◽  
Coupling System ◽  
Durability Design ◽  
Track System ◽  
Vehicle Structure

Abstract In recent years, a large number of tram–tracks have been constructed in typical soft soil area of China. Infrastructure defects due to the differential foundation settlement are serious issues in this area. To ensure the operation safety of the tram, the influence of different infrastructure defects on the dynamic response of the tram–track system has been investigated in this paper. A dynamic model of a five-module 100% low-floor tram vehicle coupled with a slab track system is developed based on a finite element (FE) method and multibody kinematics. The articulation between different vehicle modules, the wheel–rail nonlinear contact, pad failures, and a cavity in the subgrade have been taken into account in this model. The dynamic response of the vehicle–track coupling system to different operation speeds and infrastructure defects are calculated. Results indicate that the vibration energy of the vehicle body is mainly distributed in the frequency range below 1.5 Hz. This frequency range should be paid special attention in the durability design for the vehicle structure. When the number of the failure pads is larger than 3, the pad failure in tram–track has significant influence on the system dynamic response. A cavity in subgrade has a limited effect on high frequency vibrations (above 100 Hz) of the rail, while the low frequency vibrations (below 75 Hz) of the rail can be obviously increased by cavities in subgrade. The model can be used in the optimization of suspension parameters and the tram vehicle–track coupled vibration analysis.

SEA Subsystem Property Identification by Periodic FEM Approach

2011 ◽  
Vol 94-96 ◽  
pp. 1979-1982
Author(s):  
Jie Gao ◽  
Ke An Chen
Keyword(s):  
Dynamic Response ◽  
High Frequency ◽  
Periodic Structures ◽  
Low Frequency ◽  
Engineering Method ◽  
Complex Structures ◽  
High Frequency Range ◽  
Frequency Range ◽  
Remarkable Improvement ◽  
Property Identification

A study on SEA properties of periodically stiffened structure was accomplished based on the periodic theory. With application of certain software, a simulation was performed on a common periodically stiffened fuselage structure. The results indicate such modeling approach reflects relatively accurate property of subsystem in mid and high frequency range, while a remarkable improvement could also be expected in low frequency range, especially for complex structures. Such approach was approved as one reliable engineering method for solving dynamic response of periodic structures.

Comparison of the efficiency of rat papillary muscles during afterloaded isotonic contractions and contractions with sinusoidal length changes

2001 ◽  
Vol 204 (10) ◽  
pp. 1765-1774 ◽  
Author(s):  
L.J. Mellors ◽  
C.L. Gibbs ◽  
C.J. Barclay
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
Length Change ◽  
Mechanical Efficiency ◽  
Left Ventricular ◽  
Maximum Efficiency ◽  
Papillary Muscles ◽  
Work Output ◽  
Length Changes ◽  
Isotonic Contractions

The results of previous studies suggest that the maximum mechanical efficiency of rat papillary muscles is lower during a contraction protocol involving sinusoidal length changes than during one involving afterloaded isotonic contractions. The aim of this study was to compare directly the efficiency of isolated rat papillary muscle preparations in isotonic and sinusoidal contraction protocols. Experiments were performed in vitro (27 degrees C) using left ventricular papillary muscles from adult rats. Each preparation performed three contraction protocols: (i) low-frequency afterloaded isotonic contractions (10 twitches at 0.2 Hz), (ii) sinusoidal length change contractions with phasic stimulation (40 twitches at 2 Hz) and (iii) high-frequency afterloaded isotonic contractions (40 twitches at 2 Hz). The first two protocols resembled those used in previous studies and the third combined the characteristics of the first two. The parameters for each protocol were adjusted to those that gave maximum efficiency. For the afterloaded isotonic protocols, the afterload was set to 0.3 of the maximum developed force. The sinusoidal length change protocol incorporated a cycle amplitude of +/−5 % resting length and a stimulus phase of −10 degrees. Measurements of force output, muscle length change and muscle temperature change were used to calculate the work and heat produced during and after each protocol. Net mechanical efficiency was defined as the proportion of the energy (enthalpy) liberated by the muscle that appeared as work. The efficiency in the low-frequency, isotonic contraction protocol was 21.1+/−1.4 % (mean +/− s.e.m., N=6) and that in the sinusoidal protocol was 13.2+/−0.7 %, consistent with previous results. This difference was not due to the higher frequency or greater number of twitches because efficiency in the high-frequency, isotonic protocol was 21.5+/−1.0 %. Although these results apparently confirm that efficiency is protocol-dependent, additional experiments designed to measure work output unambiguously indicated that the method used to calculate work output in isotonic contractions overestimated actual work output. When net work output, which excludes work done by parallel elastic elements, rather than total work output was used to determine efficiency in afterloaded isotonic contractions, efficiency was similar to that for sinusoidal contractions. The maximum net mechanical efficiency of rat papillary muscles performing afterloaded isotonic or sinusoidal length change contractions was between 10 and 15 %.

Relaxant effect of superimposed length oscillation on sensitized airway smooth muscle

2015 ◽  
Vol 308 (5) ◽  
pp. L479-L484 ◽  
Author(s):  
Miguel Jo-Avila ◽  
Ahmed M. Al-Jumaily ◽  
Jun Lu
Keyword(s):  
Smooth Muscle ◽  
Airway Smooth Muscle ◽  
Smooth Muscles ◽  
Airway Hyperreactivity ◽  
Frequency Range ◽  
Relaxant Effect ◽  
Airway Lumen ◽  
Cross Bridge ◽  
The Cross

Asthma is associated with reductions in the airway lumen and breathing difficulties that are attributed to airway smooth muscles (ASM) hyperconstriction. Pharmaceutical bronchodilators such as salbutamol and isoproterenol are normally used to alleviate this constriction. Deep inspirations and tidal oscillations (TO) have also been reported to relax ASM in healthy airways with less response in asthmatics. Little information is available on the effect of other forms of oscillation on asthmatic airways. This study investigates the effect of length oscillations (LO), with amplitude 1 and 1.5% in the frequency range 5–20 Hz superimposed on breathing equivalent LO, on contracted ASM dissected from sensitized mice. These mice are believed to show some symptoms such as airway hyperreactivity similar to those associated with asthma in humans. In the frequency range used in this work, this study shows an increase in ASM relaxation of an average of 10% for 1.5% amplitude when compared with TO, ISO, or the combination of both. No similar finding is observed with 1% amplitude. This suggests that superimposed length oscillation acting over the interaction of myosin and actin during contraction may lead to temporal rearrangement and disturbance of the cross-bridge process in asthmatic airways.

Modified Fading Memory Model to Describe ASM Dynamics

2007 ◽  
Author(s):  
Y. Du ◽  
A. M. Al-Jumaily
Keyword(s):  
Muscle Length ◽  
Length Change ◽  
Step Change ◽  
Memory Model ◽  
Fading Memory ◽  
Frequency Range ◽  
Cross Bridge ◽  
Muscle Dynamics ◽  
Biophysical Processes ◽  
The Cross

A modified fading memory model is introduced in this work to describe the behavior of airway smooth muscle dynamics. The model is used to simulate two biophysical cases: a finite duration for the step change in length and a case for external longitudinal oscillations. For both cases, the model describes the cross-bridge behaviour well and indicates that the muscle length change is the most important factor to determine the degree of cross-bridge detachment. However, the frequency of oscillation represents the velocity of the length change, which affects the cross-bridge cycling rate as reflected in the lower frequency range. The model is intended to interpret certain biophysical processes and not to accurately model the biophysical events underlying muscle contraction.

Seismic Interaction between a Lined Tunnel and a Hill under Plane SV Waves by IBEM

2019 ◽  
Vol 19 (02) ◽  
pp. 1950004 ◽  
Author(s):  
Zhongxian Liu ◽  
Hai Zhang ◽  
Alexander Cheng ◽  
Chengqing Wu ◽  
Guogang Yang
Keyword(s):  
Dynamic Response ◽  
Low Frequency ◽  
Radiation Condition ◽  
Dynamic Interaction ◽  
Frequency Range ◽  
Seismic Safety ◽  
Reflected Waves ◽  
Diffracted Waves ◽  
Plane Sv Waves ◽  
The Hill

This paper investigates the dynamic interaction between a lined tunnel and a hill under plane SV waves using the indirect boundary element method (IBEM), with the displacement and stress characteristics of the system presented in frequency domain. The IBEM has several unique advantages such as reducing calculation dimension, automatically satisfying the infinite radiation condition, etc. The numerical results indicated that the dynamic response of the tunnel–hill system is strongly dependent on incident wave characteristics, geometrical and material properties of the lined tunnel, as well as the topography of the hill. For a dimension ratio between the hill and tunnel of less than 10.0, the lined tunnel has large amplification or deamplification effect on the dynamic response of the hill. Correspondingly, the hill also greatly amplifies the displacement and stress concentration of the tunnel especially in the lower-frequency range, due to the complicated interference effect among the reflected waves and diffracted waves induced by the tunnel and hill. Also demonstrated is that the displacement and stress amplitude spectrums highly depend on the incident frequency and the space location, and there exist multiple peaks and troughs in the spectrum curve with the peaks usually appearing in the low-frequency range. Thus, for the seismic safety assessment of a hill slope or hill tunnel in practice, the dynamic interaction within the tunnel–hill system should be taken into consideration.

Evaluation of Special Hearing Aids for Deaf Children

1971 ◽  
Vol 36 (4) ◽  
pp. 527-537 ◽  
Author(s):  
Norman P. Erber
Keyword(s):  
Hearing Aids ◽  
High Frequency ◽  
Hearing Aid ◽  
Low Frequency ◽  
Acoustic Stimulation ◽  
Deaf Children ◽  
Frequency Range ◽  
Frequency Limit ◽  
Unpublished Studies ◽  
Published Research

Two types of special hearing aid have been developed recently to improve the reception of speech by profoundly deaf children. In a different way, each special system provides greater low-frequency acoustic stimulation to deaf ears than does a conventional hearing aid. One of the devices extends the low-frequency limit of amplification; the other shifts high-frequency energy to a lower frequency range. In general, previous evaluations of these special hearing aids have obtained inconsistent or inconclusive results. This paper reviews most of the published research on the use of special hearing aids by deaf children, summarizes several unpublished studies, and suggests a set of guidelines for future evaluations of special and conventional amplification systems.

Dynamic Damping and Stiffness Characteristics of the Rolling Tire

2001 ◽  
Vol 29 (4) ◽  
pp. 258-268 ◽  
Author(s):  
G. Jianmin ◽  
R. Gall ◽  
W. Zuomin
Keyword(s):  
Dynamic Behavior ◽  
Variable Parameter ◽  
Low Frequency ◽  
Vertical Load ◽  
Frequency Range ◽  
Inflation Pressure ◽  
Vehicle Simulation ◽  
Dynamic Damping ◽  
Speed Range ◽  
Stiffness Characteristics

Abstract A variable parameter model to study dynamic tire responses is presented. A modified device to measure terrain roughness is used to measure dynamic damping and stiffness characteristics of rolling tires. The device was used to examine the dynamic behavior of a tire in the speed range from 0 to 10 km/h. The inflation pressure during the tests was adjusted to 160, 240, and 320 kPa. The vertical load was 5.2 kN. The results indicate that the damping and stiffness decrease with velocity. Regression formulas for the non-linear experimental damping and stiffness are obtained. These results can be used as input parameters for vehicle simulation to evaluate the vehicle's driving and comfort performance in the medium-low frequency range (0–100 Hz). This way it can be important for tire design and the forecasting of the dynamic behavior of tires.

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